text: magnified (pixelated)
QLineEdit's border: magnified (pixelated)

Set the QLineEdit's font to have pixel size equivalent to the height of the QLineEdit widget. Do this in the showEvent function of the class that wraps the QGraphicsView, QGraphicsProxyWidget and QLineEdit or in the showEvent function of a QLineEdit subclass. Save this pixel size to a member variable.

Detect the view scaling.

In the detection function set the pixel size of the QLineEdit's font to be equal to the cached font pixel size ( point 1) ) multiplied by the uniform view scale ( make the view scale uniform ).